Spray guns are widely used in vehicle body repair shops when re-spraying a vehicle that has been repaired following an accident. In the known spray guns, the liquid is contained in a reservoir attached to the gun from where it is fed to a spray nozzle. On emerging from the spray nozzle, the liquid is atomised and forms a spray with compressed air supplied to the nozzle. The liquid may be gravity fed or, more recently, pressure fed by an air bleed from the compressed air line to the reservoir.
One type of known reservoir consists of a rigid pot attached to the spray gun with a removable lid for filling the pot with the liquid to be sprayed onto the substrate. The reservoir is re-usable and both the spray gun and reservoir have to be thoroughly cleaned when changing the liquid in the reservoir to avoid cross-contamination which may adversely affect the finish. This is especially important when spraying part of a vehicle to match exactly the colour of the existing colour of the adjacent bodywork.
Cleaning the spray gun and reservoir is time consuming and often requires the use of solvents that are costly and may present a health hazard to the operator. In order to reduce the amount of cleaning and to facilitate changeover from one liquid to another, we have previously proposed in WO 98/32539 a reservoir in which a paint pot is provided with a disposable container received in the pot. The container comprises an open-topped liner that contains the liquid and a separate lid that closes the liner and has an outlet connectable to the spray gun.
In use the liner collapses as liquid is withdrawn from the container and, after spraying, the collapsed liner and lid can be removed and thrown away allowing a new, clean liner and lid to be used for applying a different liquid. As a result, the amount of cleaning required is considerably reduced and the spray gun can be readily adapted to apply different liquids in a simple manner. The liner, however, may collapse in a random, uncontrolled manner forming pockets in which liquid can be trapped. This can lead to some of the liquid being thrown away with the collapsed liner and lid which is wasteful.
The above-described reservoirs can be used with bulk liquids supplied ready for use such as solvents, lacquers and with liquids that are made-up on demand such as paints requiring matching of the colour to an existing paint finish. Transferring bulk liquids from a storage container is time consuming and can result in spillage which is wasteful and potentially dangerous where the liquid is flammable and/or gives of harmful vapours. Making up liquids on demand is also time consuming and can be wasteful where only a small volume of liquid is required for a given application.